Vergara - 1976 - Physiological and morphological adaptability of ri

CIJNIATE aura RICE INSEFTS 377
procedures should be applied in future research on climatic effects. It is easy
to speculate about relationships between physical and biological events. but we
need more proof and less speculation.
Field studies in Japan indicated that temperature and precipitation had little
bearing on the population regulation of .i\-'eph0retlix cincriceps (Sasaba and Kiritani.
197]). Ilouiever Kalode (1974) described weather conditions in India,
especially cessation of rainfall. that are associated with population increases of
green leathoppers (not including N. cincriceps )_ and also conditions associated
with population peaks of Nilaparvara lugens (Stal). Alam (1971), working in the
Philippines, attempted to relate climate and trends in population density of
several leathoppers and planthoppers. Each species had the largest or secondlargest
density per year in the wet season (data for l year only). Cool weather
adversely affected some populations, and .\='. lugens numbers increased when the
mean temperature increased. Light trap catches of .t\~’. hrgens in Korea were
highest under conditions of low rainfall and high temperature (Kim, 1969).
Hino et a1. (1970) noted that an infestation of N. lugens appeared to be related to
dense plant growth. low solar radiation, high relative humidity (about 90% or
more), and with little difference between day and night habitat temperatures.
Lin (1970) also measured the temperature and relative humidity within the crop
canopy. and concluded that the theoretically optimum niche for breeding and
multiplication of planthoppers was at about l0 cm above the water surface.
where both factors of the microclimate are high. and shade formed by foliage is
most effective.
Prakasa Rao. Israel, and Rao (1971) suggested that steady temperatures with
the least fluctuations between maximum and minimum, coupled with average
high relative humidity. caused outbreaks of the rice hispa (Dicladispa amiigera
Olivier) in India. Early rainfall causes early weed growth and population increase
of the insect on weeds. Then with a later dry period, the insects move on to rice.
Among other factors, mild winter temperatures and heavy rains in June and
July may have been related to the 1971 outbreak of (‘naphalocrocis medmafis
in Korea (Park et al, 1971).
Rainfall
One of the large-scale (‘Jtllbffiitlifi among rice insects is that of the oriental tinnyworm,
llfvthimnu separata (Walker), which is distributed widely in tropical
Asia. on the Chinese continent far beyond the northeast of China. in the whole
of Japan, and southwards to Fiji and New Guinea. It infests wheat. corn, oats.
and other forage crops, in addition to rice. Chu (1936) reported that the anhywonn
often had an outbreak in hot and dry years in China. On the other hand.
it has long been believed in Japan that flooded areas often suffered later from
outbreaks of the armywvonn in the paddy fields (Yamazaki, I938).
Lever (1969) analyzed. in Fiji. the relationship between outbreaks of illfyrhimna
separara, and to a lesser extent ofSpodoprer-a mam-ma (Boids) and rainfall
for the months of February and March based on official reports from 1938 to